1. Field of the Invention
The present invention relates to transmission/reception of signals in a communication system. More particularly, the present invention relates to a signal processing and transmission/reception method and apparatus for supporting analog beamforming in a digital multi-antenna system.
2. Description of the Related Art
An enhanced wireless communication system, such as a 3rd Generation Partnership Project Long-Term Evolution (3GPP LTE) system, employs digital signal processing architecture that transmits and receives signals using a plurality of antennas. In order to support a variety of use environments and conditions during the use of multiple antennas, such a wireless communication system designates or assigns transmission signals to virtual antennas called antenna ports by digital processing. The transmission signals are mapped to actual transmit antennas, and transmitted via a Radio Frequency (RF) unit and an antenna unit after being converted into analog signals. Commonly, a signal transferred to each antenna is completely processed in the digital domain, and the processing in the digital domain may flexibly apply a variety of multi-antenna algorithms that support a plurality of codewords and a plurality of layers. However, the conventional wireless communication system may not employ more antennas, since it employs only the digital signal processing method to use multiple antennas. Because the number of available antennas is limited, the available antenna gain is also limited.
Analog beamforming technology used in a communication system that supports relatively static stations, as in the Institute of Electrical and Electronics Engineers (IEEE) 802.11ad standard, may support a very large number of antennas and control beams using phase shift values or switches in an analog unit. The analog beamforming technology shifts a phase of one analog signal by means of an RF unit, and transmits the phase-shifted signals via NT antennas. This analog beamforming (or RF beamforming) may significantly increase the antenna gain with the use of a very large number of antennas, but its performance may be limited because its digital unit may not employ various digital antenna signal processing technologies, including digital beamforming. In addition, the analog beamforming technology supports only Time Division Multiplexing (TDM), but does not support Frequency Division Multiplexing (FDM).
This conventional technology either employs multi-antenna technology by digital signal processing, or performs analog beamforming by controlling an analog unit. Therefore, it is unable to obtain the benefits of the two different technologies. Therefore, a new technology is needed to efficiently support both the multi-antenna technology by digital signal processing and the analog beamforming.